From 2004 to 2009, the average U.S. national wastewater treatment rate increased by 28%. There are approximately 18,500 municipalities in the United States producing 40 billion gallons of wastewater per day at a taxpayer cost of $150,000,000 or $55 billion dollars annually. A study by the Association of Metropolitan Sewage Agencies indicates that 25% of this 40 billion gallons per day, or $14 billion annually, is due to inflow and infiltration of ground and storm water, the cause of which is directly linked to an aging and faulty sewer infrastructure.
For calculation of flow in an open channel that is gravity fed, a well established method is used. This method, known as the Mannings equation, allows a flow value to be derived by first knowing certain conditional parameters of the application. One of the parameters is the roughness of the channel material usually obtained by an empirically derived table of constants. Another parameter is the slope of the channel specified in percentage of horizontal length to vertical drop. These parameters may be difficult to obtain with any certainty or may require stopping flow, which may not be practical for meter site installation.
The base Circular Mannings equation is in the form of:
  Q  =            1.49      *      A      *              R                  2          /          3                    *              S                  1          /          2                      n  Where A is the area of flow, R is the hydraulic radius, S is the slope of the pipe and n is the roughness coefficient of the pipe. Unfortunately, heretofore during meter installation, it has typically been required to go into a confined space area to get measurements required for accurate flow calculation. This created a potential safety risk and required special equipment and permits.